An electrical or power substation involves electricity transmission and distribution systems where voltage is transformed from high to low or the reverse using transformers. Electric power may flow through several substations between generating plant and consumer or load, and the voltage may be transformed in several steps.
Industrial setups involve intense energy consumption and include one or multiple dedicated substations including both upstream substation connecting to the main source of power (either the grid or the in-house generator) and downstream substations for distribution of power to different load centers distributed over various parts of industries. In addition, the industry may have its own generation system to meet its energy demand and also have power management system for effectively handling power for its purpose.
Power management functionality includes load shedding, power and voltage control, power restoration, power source synchronization etc. that depend on measurements like voltage, current, power and other power-quality parameters for effective handling of power demands for various equipment and processes, power fluctuations, equipment constraints etc. It is becoming common to find these kinds of power management needs within industrial setups like process industries such as refineries and power utilities. However, such setup is also applicable to other process industries such as cement, pulp and paper, petrochemical plants, fertilizers, steel, mining and metals, water and waste water treatment plants etc.
The substations (both upstream and downstream) can include equipment such as several power and distribution transformers, cabling, switching, reactive power and grounding equipment. This equipment should be protected against power system anomalies like power surges, power system faults etc. This can be addressed by Intelligent Electronic Devices (IEDs) that provide different comprehensive protection and monitoring functions. Besides protection and monitoring functions, IEDs also offer metering and control functions. The IEDs are microprocessor-based devices that are associated with power system equipment, such as circuit breakers, generators, transformers, power lines, power cables, reactors, motors, capacitor banks etc. The IEDs can receive primary power system information like voltage and current from sensors to perform various protection and monitoring functions. Exemplary types of IEDs include protective relaying devices, load tap changer controllers, circuit breaker controllers, recloser controllers, voltage regulators, secondary function (like load shedding etc, where the load shedding functionality is implemented in an IED and process data exchange for such a functionality is done by the primary IEDs that directly interface with the power system equipment, controllers etc.). Thus, an IED can perform several power system functions depending on its purpose.
Substation automation can be an important and complex aspect to solve the power system function tasks, using state of the art technologies. By doing so, Substation automation also provides value added features to perform automatic control based on power system conditions/events, equipment maintenance, communication of substation information to higher level control systems like Grid Control Centers etc. Through the Substation automation, manual and automatic control command functions are provided like closing and opening of switching equipment (circuit breakers and disconnectors), or raising/lowering voltage levels in order to maintain the desired voltage levels. Multiple communication protocols exist for substation automation, which include many proprietary protocols with custom communication links. However, interoperation of devices from different vendors is highly desired for simplicity in implementation and use of substation automation devices.
The IEC61850 standard from International Electrotechnical Commission (IEC) advocates interoperability amongst Intelligent Electronic Devices (IEDs) from various manufacturers using common engineering models (for example, IEC61850 Common Engineering Model using Logical Nodes), data formats and communication protocol. Recent IEDs are therefore designed to support the IEC61850 standard for substation automation, which provides interoperability and advanced communications capabilities like GOOSE (Generic Object Oriented Substation Event) and MMS (Manufacturing Message System) communication profiles.
The power management functionality like load shedding, is currently implemented as a centralized function in the substation automation systems for process industries like refineries, petrochemical plants, steel plants, cement, pulp and papers etc. The load shedding or shedding of load referred herein can involve cutting off the power on certain lines/loads, when the power demand becomes greater than the power supply. This can take place on the occurrence of a power system fault or an event that would affect the power available to feed the processes in an electrical network.
Centralized implementation of the above function, for example, implemented in a single process controller IED and deployed at the upstream substation, has several short comings. For example, centralized function implementation causes high loading due to centralization of all functions for the complete power system network, where load shedding is to be deployed. It also results in high and sustained levels of communication loads in the process controller IED, as it would collect desired data from downstream IEDs for execution of the centralized function. This leads to lower availability of the process controller IED for other activities. Since the downstream IEDs are directly connected to the central process controller, it is directly exposed to the complexity of the substation configurations and connectivity.
Further, there are limitations in coverage in case of high number of islanded networks (power network that gets isolated from upstream substation due to a fault in the network) in the substation as only a particular number of islands can be handled by the centralized controller. The undetected islands are thus left vulnerable to system disturbances, without the ‘coverage’ of the centralized load shedding function.
Also, overload situations in a downstream transformer cannot be easily detected in the centralized implementation and hence there may be no facility for downstream substation slow load shedding to lessen overloading on the transformers. The loads can be manually shut down due to lack of any intelligent load shedding action in the downstream substation. This results in a lack of discrete isolation of loads, thereby lessening system availability.
Hence the present disclosure is directed to, for example, a power management system and technique that allows for improved and distributed power management as an alternative and efficient solution against central power management systems and methods currently available.